Self-baking electrodes are known. This type of electrode is made by baking a carbonaceous paste in conjunction with operation of an electric arc furnace, which receives the baked electrode. An early such electrode is shown in U.S. Pat. No. 1,442,031 (Soderberg), which includes a container for holding electrode paste and bakes the paste by heating it. Unbaked electrode paste cannot carry a large electric current, but the baked paste is capable of carrying substantial electrical current and is used for supplying the large amounts of electric current required for operation of electric arc furnaces. Applicant's prior U.S. Pat. No. 4,756,813 teaches a self-baking electrode wherein electric current, both for operating a furnace and baking the paste, is supplied to the paste through a centrally-located mandrel. U.S. Pat. No. 3,524,004 (Van Nostran et al.) also shows supply of electric current to the center of the electrode to bake the paste and supply of a portion of the current required by the furnace to the exterior of the electrode. U.S. Pat. No. 4,527,329 (Bruff) shows a process for manufacture of a furnace electrode in situ where heat for baking the paste is supplied independently of the current operating the furnace.
Further, it is known to extrude a self baking electrode by application of pressure to the electrode paste, as shown in applicant's prior U.S. Pat. No. 4,756,004. While the structure shown in this patent is useful, the baked electrode is susceptible to inadequate baking on the one hand and becoming stuck in the housing on the other.
Known methods for making self-baking electrodes have not been successful, primarily because of the difficulties arising from the interaction between the baking zone and the various parts of the baking apparatus. The Van Nostran apparatus, for example, uses a screw to advance the baked paste, but strong adherence between the screw and the baked paste eventually results in an inability to continue advancing the electrode and consequent failure. Similarly, production of self baking electrodes in accordance with applicant's prior patents has been problematic because of the adhesion between the baked paste and the paste container.